A magnetic disk device has a data recording area, which is set on a disk-like magnetic recording medium rotated around a spindle, and a head, wherein data read/write is conducted by moving the head in the data recording area. The magnetic disk device is also provided with an inner stopper for preventing the head from coming into contact with the spindle during data read/write operation or a ramp load for retracting the head when the device is stopped.
Some of the magnetic disk devices include an outer stopper for preventing the head from contacting with the wall surface of the magnetic disk device casing. Furthermore, the ramp load can be located on the inner periphery (spindle) of the disk-like magnetic recording medium or on the outer periphery (wall surface of the disk device casing).
The conventional recording areas have been determined by setting as a constant standard a range in which the head is not brought into contact with the spindle or ramp load during data read/write operation and employing this standard for all the disk drives. The area outside the range serving as the standard is provided as an extra area.
However, a mechanical tolerance such as stopper installation conditions, head installation direction, and ramp load installation position differ between the magnetic disk devices. Therefore, the first problem was that in some disk devices, if a constant standard was applied, the area on the magnetic recording medium that can be used as a data recording area was provided as an extra area.
Further, in the magnetic recording medium a plurality of circular tracks are set concentrically and a plurality of sectors, which are the data recording units, are set in the tracks. Because the length of a circumference is proportional to its radius, the length of the circumference on the outer periphery is larger than that on the inner periphery and the recording linear density (the volume of recorded data per unit length) on the outer periphery is less than the recording linear density on the inner periphery, provided the data transfer ratio is the same. Here, a method for recording the data on the outer periphery with the same recording linear density as on the inner periphery is employed to record a larger volume of data on a single magnetic recording medium.
With this method, the recording angular density of the outer peripheral zone is increased and the recording linear density is made almost uniform between the inner periphery and outer periphery by dividing the magnetic recording medium into a plurality of concentric circular zones by track boundary lines and by varying the frequency used for recording in each zone. A high magnetic angular density means larger number of sectors contained in each zone, on the outer peripheral side.
However, in recent years a demand was created for large-capacity magnetic disk devices, and devices have appeared with a high recording linear density that has to be attained by the head and with a high recording angular density that increases toward the outer peripheral zones to obtain a uniform linear density between the inner periphery and outer periphery. Furthermore, in order to determine the data recording area by employing a constant standard for all the magnetic disk devices, it was necessary to set automatically the recording linear (angular) density that has to be attained by the head in order to realize the prescribed capacity and to select heads according to the same standard for all the heads.
On the other hand, the head production technology has not been accordingly advanced, and at the present level of head production technology the produced heads have a large spread of characteristics. Therefore, the second problem was that the degradation of yield in head production caused by the fact that the recording linear (angular) density of the head did not meet the required standard could not be improved.